Sustained release from chitosan microspheres encapsulated multiparticulates

Abstract

The multiparticulates of chitosan microspheres were prepared by the spray drying and solvent evaporation methods. Microcore was consisted of chitosan or maltose-g-chitosan, while poly(octadecyl acrylate-co-acrylic acid) was used as matrix. Chitosan-g-maltose was synthesized by reductive amination. Methanol was used to control the grafting yield by adjusting the maltose solubility and the grafted chitosan was confirmed by NMR and FTIR spectroscopy. Poly(octadecyl acrylate-co- acrylic acid) was prepared by free radical polymerization using benzoyl peroxide as initiator in toluene. After forming microcores, multiparticulates were prepared by solvent evaporation and by spray drying method of dispersion of microcores. The morphology and size of microcores depended on the preparation conditions and the degree of maltose graft. The size of microcore was small (4-10). The morphology and particle size of multiparticulates also depended on nature of microcore, matrix composition and preparation method. The release from microcores and multiparticulates was investigated. Chitosan microspheres released the calcein very quickly at pH 2.0 and in 10hr at pH 7.0. Release was controlled by maltose graft and by crosslinking. Chitosan-g-maltose microspheres release the drug much faster at pH7.0. Crosslinked microspheres showed slower release. Release from the multiparticulates depend on the property of microcores and matrix composition. Chitosan-g-maltose microspheres encapsulated multiparticulates showed faster release at pH 7.0 and 12.0.